Weatherford has drilled one million feet with its Revolution rotary-steerable system and along the way has set new milestones for some of the deepest, hottest, highest-pressure environments encountered in the E&P sector.
Rotary-steerable systems (RSS) outperform conventional directional systems by significantly improving the drilling process through better hole cleaning, higher rates of penetration (ROPs), precise directional control and extended reach of horizontal wells.
Weatherford’s Revolution RSS uses “point-the-bit” technology to deliver a gun-barrel in-gauge wellbore. The high-quality wellbore provides significant benefits, including improved formation evaluation, reduced drilling-fluid costs, easier installation of tubulars and enhanced production.
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Point-the-bit technology has been proven to drill a much straighter and smoother hole than competitive “push-the-bit” systems.
Enhancing the capabilities of the Revolution system is Weatherford’s logging-while-drilling (LWD) system, which provides key downhole data to optimise wellbore placement.
A better system for LWD
Weatherford’s PrecisionLWD system components are entirely new generation, designed from the outset to handle tough drilling conditions.
The hostile-environment logging (HEL) measurement-while-drilling (MWD) system transmits basic positional measurements in real time, while the total PrecisionLWD system includes all HEL MWD components plus multi-frequency resistivity, thermal neutron porosity and azimuthal density sensors.
Of course, it is not enough to measure what is going on down in the borehole. The data must also be conveyed to the surface. LWD tools rely on sending data as pulses in circulating drilling mud.
If the mud is not circulating or is aerated (as in most Controlled Pressure Drilling scenarios), it will not transmit a pulse.
To overcome this obstacle, the PrecisionLWD system is the only triple-combo system in the industry that can use electromagnetic (EM) technology, which transmits data by sending data pulses electrically through the earth rather than through the drilling mud.
Weatherford’s system can acquire data at logging speeds of 400 feet (122 metres) per hour, achieving one of the industry’s highest data-acquisition speeds in an LWD triple-combo system. This means that LWD operations can now contribute positively in high-ROP drilling environments.
Milestone 1: Deepest well, highest pressure
In the Green Canyon section of the Gulf of Mexico, a major operator was drilling a vertical exploration well from a drillship, the daily operating costs of which approached US$500 000.
At close to 29,000 feet (8,839 metres), the 8 1/2-inch hole started to drift away from the vertical position.
To solve the problem, Weatherford deployed the Revolution RSS with the HEL MWD and PrecisionLWD systems, and within 24 hours drilling was once again back on target. Successfully operating the Revolution RSS at this extreme pressure and depth remains a Gulf of Mexico drilling record.
The well ultimately reached total depth at more than 34 000 feet (10 363 metres)-nearly 6.5 miles, or 10.4 kilometers. This achievement broke the previous record depth of 32 727 feet (9,975 metres)-6.2 miles, or 10.0 kilometers-set earlier in 2005 by Shell, which also used the PrecisionLWD system.
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The RSS and LWD systems performed without incident, transmitting real-time data at 99% pulse efficiency and recording triple-combo log data in these extremely hostile conditions.
(Temperatures reached 280°F, or 138°C, and pressures exceeded 30 000 pounds, or 207 megapascals, the official pressure rating of the LWD system.)
Using a conventional mud motor rather than the Revolution RSS to bring this well back to vertical would not have been successful, say the operator’s engineers involved in this project.
The Revolution RSS saved millions of dollars in rig operating costs and accomplished the drilling objectives without failure.
Milestone 2: Rising temperatures
As wells go deeper, temperatures rise. The PrecisionLWD system was run in 2007 on two deep, high-temperature directional wells in one of the most challenging drilling environments offshore India.
The first of these wells encountered severe lost-circulation problems, which resulted in the loss of cooling effect from the circulating fluids.
After the well was brought back under control and normal circulation resumed, the PrecisionLWD system was still functioning normally, having recorded a maximum temperature of 349°F (176°C).
The system was pulled from the hole, and the LWD memory was downloaded to retrieve temperature and pressure data, which helped the operator understand the downhole events that occurred during the lost-circulation event.
The operator is now using the data to develop a detailed knowledge base for future wells in the area.
While 349°F is remarkable, that record was surpassed recently by a well in the Gulf of Mexico that was successfully drilled and logged at a temperature of 383°F (195°C)-almost twice the boiling point of water.
Middle East milestone: Toughest doglegs
The PrecisionLWD system recently helped revive a mature field in the Middle East through an ambitious high-angle, short-radius re-entry drilling program.
The goal was to drill out of existing vertical wells, turning quickly to horizontal extensions that could reach bypassed pockets of oil.
With these tough doglegs, the wells would be much more challenging to drill, but they would be able to enter the target formation closer to the vertical wellbore.
In some cases the kickoff could take place right within the pay zone.
Motor and MWD technologies were used to aggressively drill the build sections, but other LWD services could not be used to geosteer the important horizontal reservoir section because competitive LWD systems could not survive the trip through the high-dogleg build sections. Not so with the PrecisionLWD system.
Used in 2006 in nine wells, this system was pushed through maximum dogleg severities ranging from about 49 to more than 61 degrees per 100 feet (30 metres), then used to effectively drill and log the horizontal sections.
The lateral extensions drilled out of the short-radius build curves ranged from just over 1,000 feet (305 metres) to almost 3,000 feet (914 metres).
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Sidetracking plugged wells and re-completing the short-radius horizontal sections enabled the operator in the Middle East to produce additional reserves, increase ultimate recoveries (a benefit of geosteering accuracy) and extend the productive life of the field-a great model for brownfield rejuvenation.
Middle East milestone 2: Water injection well
A major operator in the Middle East had a problem with one of its reservoirs in a mature and depleting field. The operator wanted to drill water-injection wells underbalanced (UB) to reduce bottomhole pressure and resultant formation damage (which typically required extensive acid stimulation).
But the aeration of the mud in UB drilling meant that mud-pulse transmission of LWD data would not be possible. This project would be the first trial of Weatherford’s EM LWD in an underbalanced well-and it worked.
With mud-pulse transmission, the mud must be pressurised and circulating; and in this state, monitoring static pressure is impossible. But a key advantage offered by EM transmission was the ability to monitor the static pressure of the well in real time before drilling UB.
This capability, in turn, allowed fine-tuning of fluid rates and injection to match well conditions.
EM transmission also provided high-quality real-time steering data while drilling ahead at 150 feet (46 metres) per hour; and well surveys could be taken while making up drillpipe connections, saving rig time.
Result: 3,018 feet (920 metres) of reservoir section was drilled UB in one bit run while maintaining UB conditions and good hole cleaning and while acquiring full gamma ray, resistivity, density and neutron logging data.
Milestone 5: Longest extended-reach well in the Al Jurf field
An operator in Libya wanted to drill a long, 6 1/2-inch lateral in the Al Jurf field offshore Libya, but previous attempts had been unsuccessful.
Drilling with a mud motor past 12,000 feet (3,659m) was difficult because sliding the drill bit forward-necessary to reposition the mud motor-was impossible beyond 11,873 feet (3,619m).
The solution: Weatherford RSS
The solution was Weatherford’s Revolution RSS and a move up from 3 1/2- to 4-inch drillpipe.
The Revolution system was brought in for the build and the lateral, drilling to a total depth of 15,569 feet (4,745 metres).
The ROP through the El Gueria limestone averaged 31.2 feet (9.5 metres) per hour in the build section (which included a 16-degree left-hand turn) and 29.5 feet (9.0 meters) per hour for the entire section.
The record depth set for this well exceeded that of the previous well by 2 411 feet (735 metres) and gave the operator access to reserves that had previously been unreachable.
The Revolution RSS and PrecisionLWD systems are designed specifically for directional, extended-reach, short-radius performance in deeper and hotter drilling environments.
Providing services from the routine to the extreme, these Weatherford tools are technological enablers that can help turn brownfields green again.
